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Keithley 2268-40-21

DC Power Supply with USB, LAN, GPIB, RS-232, RS-485, and Analog Interfaces, 40V/21A/850W

Brand: Keithley
Model No: 2268-40-21
Our Model No: 22684021
Condition: NEW
PDF Document Icon Data Sheet (387 KB)

Replaced By:

Product Features:

  • 40V maximum voltage
  • 21A maximum current output
  • 850W maximum power
  • Compact 1U, half-rack enclosure provides highest power in smallest package
  • Two auxiliary outputs support driving or signaling external devices, often eliminating need for additional instrumentation
  • Isolated analog inputs minimize control line noise
  • Built-in LAN, USB, GPIB, RS-232, RS-485 interfaces and analog inputs
  • Constant voltage, constant current, and constant power setting control
  • Auto sequence control supports internal execution of commands to minimize bus communication time
  • Control up to 30 supplies through a single controller interface
  • Foldback mode with programmable delay shuts down output on transitions between CV and CC operation to protect voltage- or current-sensitive devices
  • Numerous safety features protect the load and the supply, including: over-voltage and under-voltage protection, over-current protection, over-temperature protection, loop protection for multiple-supply configurations, and hardware output interlock


  • Production testing
  • Environmental testing
  • Accelerated life testing
  • Process control systems

The Keithley 2268-40-21 40V/21A/850W DC Power Supply offers the highest power density in the smallest package. The 2268-40-21 is packaged in a low profile 1U high, half-rack width enclosure. It takes up minimum space in a test rack. When multiple supplies are needed, the 2268-40-21 can easily mount side-by-side in a test rack to provide two outputs in a 1U height space. Ventilation for the 2268-40-21 is from the front of the instrument to the back, so that additional rack space for airflow above, below, or to the side of the supply is not required. Thus, only 1U of total rack height is all that is needed. Furthermore the 2268-40-21 operates at temperatures up to 50 deg. C so that they can perform reliably even in test racks that have elevated temperatures.

A Full Complement of Control and Interface Options

The 2268-40-21 offers users a wide range of interface options, including built-in LAN, USB, GPIB, RS-232, and RS-485 control interfaces. It can also be controlled by analog control signals. A supply's voltage output and current can be set using either voltage or resistance input values.

Both isolated and non-isolated analog inputs are available. When long control lines or control lines exposed to an electrically noisy environment create signal integrity concerns, the isolated analog inputs can reduce or eliminate the susceptibility to signal degradation.

An auto sequence program mode gives the 2268-40-21 the built-in intelligence needed to execute lists of commands. Multiple commands can be downloaded, stored in the power supply's memory, and executed using a single command from the controller. The program can be repeated a specific number of times or cycled continuously. This ability to execute a set of commands internally saves test time by eliminating the delays involved in sending individual commands over a PC bus.

For large power systems that require multiple power supplies, up to 30 Series 2268 supplies can be controlled through a single interface by linking all the supplies together through their RS-485 interfaces. That allows controlling all the supplies through a master unit, which can use any of the five standard PC interfaces. This greatly simplifies managing multiple power supplies in a single system.

Auxiliary Outputs for External Device Control

In addition to the main output power, 2268-40-21 offers two auxiliary outputs, 15V output and a 5V output, for signaling and control tasks, such as to supply signals to a device handler or a test fixture control input. These auxiliary outputs can also drive external control relays. For test systems that require a few control signals or relay control, these outputs can eliminate the need for another power supply or data I/O card.

Use a Series 2268 DC supply as part of a control system. Analog control signals can program the supply's output. In addition to driving the load, the supply's two auxiliary outputs can drive external devices or circuits. The auxiliary outputs can eliminate the need for extra power sources in a test system. Interlock connections can turn off the supply's output if an unsafe external condition is detected.Click for larger image

Control System

Control up to 30 Series 2268 power supplies through one interface to a master supply. The additional supplies are daisy-chained to the master through serial RS-485 connections.Click for larger image

Master Supply

Expand Voltage or Current Capacity for Higher Output Requirements

For test applications that require a higher voltage or current output than a single supply can produce, up to two 2268-40-21's can be connected in series or up to four of them connected in parallel to produce the required output. Using the analog control lines, the supplies can be arranged in a master-slave configuration. The safety settings for the master supply control the complete configuration of supplies so that all supplies are protected.

When an application requires a bipolar output, two 2268-40-21's can be linked with the low terminal of one supply connected to the high terminal of the second one. This connection can be tied to the common of the bipolar load; one supply produces a positive output and the second supply effectively produces a negative output.

Protection for the Load and the Power Supplies

The S2268-40-21 provides one set of parameters designed to protect the load from damage and another set that protects the supply, itself. For applications that require outputting voltages only within a narrow range, the 2268-40-21 supports setting both over-voltage and under-voltage shutdown levels. Over-current protection prevents excess current from damaging the load, the supply, or both. An over-temperature limit prevents excessively high temperatures that could damage the supply's internal components.

The 2268-40-21 incorporates a standard foldback function which, when enabled, will turn the output off, if the load condition causes the supply to switch between the CV and CC control modes. In addition, this power supply adds a programmable delay time to the foldback function to allow a time delay before the output is turned off. Thus, if the supply is powering a load with a high in-rush current which is large enough to cause the supply to switch to the CC mode from the CV mode, the delay would prevent the foldback function from an unwanted shutdown of the output so that the load stays powered and reaches its steady-state current level. If an external interlock circuit loses continuity, the hardware output interlock can be used to turn off a supply's output. Input/output lines allow external shutdown control and provide an output on/off status.

For test systems that integrate multiple Series 2268 supplies, loop protection allows up to four supplies to be shut down as a group; there is no need to shut down the whole system.

  • 1 - Single-Output DC Power Supply
  • 1 - User Manual CD
  • 1 - AC Line Power Cord
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Datasheet: PDF Document Icon(387 KB)
Manual: PDF Document Icon(8.87 MB)
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